The invention relates to a charging/discharging station for charging or discharging an at least partially battery-operated vehicle via an inductively coupled pair of coils. A method for operating such a charging/discharging station is also provided.
As an alternative to charging or discharging using a cable (so-called conductive charging), inductive charging is an innovative solution for charging or discharging at least partially battery-operated vehicles, in particular electric vehicles. Inductive charging does not require any intervention by the vehicle user, that is to say a plug does not have to be inserted in particular, and there is a certain amount of protection against weathering influences and vandalism since the relevant components, in particular a primary coil, can be inaccessibly embedded in the road surface or can be included in a charging plate placed on the road surface. The primary coil is connected to the power supply system by means of suitable electronics. A secondary coil is typically permanently mounted in the underbody of the vehicle and is in turn connected to the vehicle battery by means of suitable electronics. In order to transmit energy, the primary coil generates a high-frequency alternating magnetic field which permeates the secondary coil and induces a corresponding current there. Since the power which can be transmitted is typically scaled linearly with the switching frequency and the switching frequency is limited by the control electronics and by losses in the transmission path, a frequency range of approximately 20 to 150 kHz results.
During inductive charging, energy is transmitted via the air gap between the coils. In order to transmit energy as efficiently as possible, the highest possible degree of coupling between the two coils is required. With an increasing offset between the coils, the losses increase and the efficiency is reduced. In addition, a strong stray field, a field which emits freely and is not caught by a receiving coil, that is to say the secondary coil, may result in health risks and safety problems. A central challenge with inductive charging is therefore that of positioning the primary coil and the secondary coil in an optimum manner with respect to one another.